Why is there a ring around the moon before bad weather? And what causes it?
The ring around the Moon is caused by the reflection of Moonlight (which of course is reflected sunlight) from ice crystals in the upper atmosphere. Folklore has it that a ring around the moon signifies bad weather is coming, and in many cases this may be true. How? The ice crystals that cover the halo signify high altitude, thin cirrus clouds that normally precede a warm front by one or two days. Typically, a warm front will be associated with a low pressure system which is commonly referred to as a storm.
